Oseltamivir-resistant influenza A(H1N1) pdm09 virus: first reported case from India

ABSTRACT

Background: Recent studies on antiviral susceptibiliy from South-East Asia,Europe and the United States have shown sporadic neuraminidase inhibitor (NAI)resistance in A(H1N1)pdm09 viruses. We undertook a study to evaluate NAIresistance in these viruses isolated in India.Methods: Pandemic influenza viruses, isolated from 2009 to 2013, along withclincal samples were genetically analysed for known resistance markers in theneuraminidase (NA) gene. Clinical samples (n=1524) were tested for H275Y (N1numbering; H274Y in N2 numbering) mutation by real time reverse transcriptasePCR (rRT-PCR). One hundred and ten randomly selected resistant and sensitiveviruses were analysed by phenotypic assay.Results: All but one of the 2013 A(H1N1)pdm09 isolates were sensitive tooseltamivir. Genetic analysis of this isolate as well as the original clinical materialshowed that the presence of H275Y mutation was responsible for reducedsusceptibility to oseltamivir in the patient. This was confirmed by phenotypic assay.Conclusion: The emergence of a pandemic influenza strain resistant to oseltamiviremphasizes the need for monitoring antiviral resistance as part of the NationalInfluenza Programme in India